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1.
Excited states in 188Tl have been studied experimentally using the 157Gd (35Cl, 4n) reaction at a beam energy of 170MeV. A rotational band built on the πh 9/2 ⊗ νi 13/2 configuration with oblate deformation has been established for 188Tl. Based on the structure systematics of the oblate πh 9/2 ⊗ νi 13/2 bands in the heavier odd-odd Tl nuclei, we have tentatively proposed spin values for the new band in 188Tl. The πh 9/2 ⊗ νi 13/2 oblate band in 188Tl shows low-spin signature inversion, and it can be interpreted qualitatively by the two-quasiparticle plus rotor model including a J-dependent p-n residual interaction.  相似文献   

2.
The absorption of the tunable narrow-band laser radiation with λ = 276.9 nm at the 62 P 1/2 → 62 D 3/2 transition in the atomic thallium beam is experimentally studied. The isotopic selectivity and efficiency of the excitation of the 62 D 3/2 state is investigated. The splittings between the 203Tl and 205Tl isotopes were found to be Δv = 0.98 and 1.25 GHz for the transitions with the nuclear momenta F = 1 → F = 1, 2 and F = 0 → F = 1, respectively, which is sufficient for a relatively high isotopic selectivity of the 62 D 3/2 state excitation with the subsequent ionization for the laser separation of the thallium isotopes. The effects that lead to the broadening of the resonance and a decrease in the selectivity are analyzed. The main contribution is related to the field broadening by the laser radiation, which limits the mean laser power density.  相似文献   

3.
Anti-Stokes Raman laser experiments using metastable atomic Tl and Sn have been performed. The required metastable population inversion is generated by photodissociation of TlI and SnBr2 with KrF laser radiation. The Tl(Sn) system permits frequency up-conversion by 7793 cm–1 (17,163 cm–1). By optimization of system parameters, uv output energies up to 2.5 mJ (377 nm) and conversion efficiencies of more than 25% have been achieved for Tl. Further improvements and principal limitations will be discussed.  相似文献   

4.
The /EC decay of 189m, gPb has been studied at the ISOLDE facility using nuclear spectroscopy and in-source laser spectroscopy. A level scheme of 189Tl has been built from - coincidence relationships and information on the feeding of some excited levels of 189Tl provided by the hyperfine spectra obtained from laser ionization. The half-lives of both the 13/2+ and 3/2- 189Pb isomers have been estimated to be T 1/2 = 50±3 s and T 1/2 = 39±8 s, respectively. Calculations have been performed for different oblate and prolate nuclear deformations using an axial-rotor coupled to one-quasiparticle model, a structure has been suggested for the low-lying levels of the 189Tl nucleus.  相似文献   

5.
High-spin states in 190Tl have been studied via the 160Gd(35Cl, 5nγ) reaction. The level scheme, consisting of the πh 9/2vi 13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly assigned to the oblate band in 190Tl, resulting in low-spin signature inversion in the πh 9/2vi 13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the oblate bands in 192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including p-n residual interactions.  相似文献   

6.
The hyperfine structure, isotope and isomeric shifts in the atomic transition 6p 2 P 3/2–7s 2 S 1/2, =535 nm have been measured for theI=7 andI=2 states of190, 192, 194, 196Tl; theI=1/2 andI=9/2 states of191Tl and the I=7 isomer of188Tl. The thallium isotopes were prepared as fast atomic beams at the GSI on-line mass separator following fusion reactions and — in some cases — subsequent-decay. The nuclear dipole moments, electric quadrupole moments and the change in the nuclear mean square charge radius are evaluated. Theuu-isotopes show an isomeric shift which changes sign between192Tl and194Tl.Dedicated to P. Armbruster on the occasion of his 60th birthday  相似文献   

7.
Preparation of superconducting Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba2Ca2Cu3Ox thin films is reported. From a sintered Ba2Ca2Cu3Ox bulk sample we prepared using a pulsed Nd:YAG laser, Ba-Ca-Cu-O thin films on sapphire and SrTiO3 single-crystal substrates. Subsequently the films were loaded with Tl by simultaneously annealing the films together with a sintered Tl2Ba2Ca2Cu3O10 sample both enclosed in a small stainless steel box; in our procedure Tl contamination was reduced to a minimum. Tc values near 100 K and critical currents of 5·103 A/cm2 at 77 K were obtained.  相似文献   

8.
The time resolved polarized CARS technique has been used to detect Cl atoms produced by photolysis of ICl in the presence and absence of O2. A population inversion was observed between the ground state electronic levels Cl(2 P 1/2) and Cl(2 P 3/2). The rate constant for Cl(2 P 1/2) decay (quenching + reaction) in ICl was determined to be (3.2±0.2)×10–13 cm3/molecule×s; the rate constant for Cl(2 P 3/2) reaction with ICl was determined to be (7.8±0.5)×10–12 cm3/molecule×s; and the rate constant for Cl(2 P 1/2) quenching by O2 was determined to be (1.9±0.2)×10–13 cm3/molecule×s.  相似文献   

9.
瞿定荣  范凤英  宋增云 《物理学报》2014,63(3):32801-032801
本文对光化学法分离中氩气对2P激发态锂原子的碰撞猝灭速率进行研究.在弱激光作用下,通过对不同氩气压强下的锂原子蒸气吸收光谱和激发态锂原子的荧光发射光谱进行测量,得到氩气对2P激发态锂原子的猝灭速率常数为(12.29±0.92)×10-18m3·s-1.实验结果表明:在光化学锂同位素分离研究中,氩气对锂原子2P激发态的猝灭速率远小于2P激发态锂原子的自发辐射速率,碰撞猝灭效应对分离选择性的影响非常小,可以忽略不计.  相似文献   

10.
New values of a number of kinetic constants of processes proceeding in oxygen-iodine laser media are presented. The total probabilities of formation of I2(X, 15 ≤ v ≤ 24) and I2(X, 25 ≤ v ≤ 47) molecules in the course of quenching of I* atoms by I2(X) are found to be 0.9 and 0.1, respectively. The quantum yield of singlet oxygen in the reaction O(1 D) + N2O → N2 + O2(a 1Δ) is close to 100%. The quenching rate constants of I2(A’) by O2, H2O, CO2, I2, and Ar and of I(2 P 1/2) by O(3 P), O3, NO2, N2O4, and N2O are presented.  相似文献   

11.
Efficient cw intracavity frequency doubling of a diode-end-pumped Nd:YAG laser operating on 4 F 3/24 I 9/2 transitions at 946 nm has been demonstrated. A symmetrical cavity with two composite laser rods was designed, which divides the pump power between the two composite laser rods, allowing for greater power scalability. A 30-mm-long LiB3O5 (LBO) crystal, cut for critical type I phase matching at 57 °C, was used for the intracavity frequency doubling of the laser. A maximum output power of 3.8 W in the blue spectral range at 473 nm has been achieved at 39 W of pump power. The beam quality M2 value is 2.3 in both horizontal and vertical dimensions. PACS 42.55.Xi; 42.65.Ky  相似文献   

12.
 Quenching of fluorescence from Na(32 P) and K(42 P) atoms by various collision partners was studied at 973 and 1273K. Excited alkali atoms were produced photolytically by excimer laser light at 193nm. For each collision pair, the appropriate relative velocity was computed and used to evaluate the quenching cross-section from the measured rate constants. Cross sections for CO2, O2 and N2 are large (10–60Å2) while for Ar, the values are <1 Å2. The results are compared with those of previous investigations as a function of relative velocity. Finally, implications for combustion diagnostics are briefly discussed. Received: 29 March 1996  相似文献   

13.
A new 1223-type (Tl, V)-based superconducting layered cuprate (Tl1–x V x ) Sr2Ca2Cu3O9 withx=0.25 and 0.50 has been successfully synthesized in the nearly-pure form and identified by powder X-ray diffration analyses. An excessive quantity of Tl is necessary for the preparation of the (Tl, V)-based 1223-type compound. Resistance and ac susceptibility measurements showed that the new (Tl, V)-based 1223 cuprate exhibits Tc above 110 K.  相似文献   

14.
We report on the synthesis and a structural investigation of two isomorphous variants of (Tl, Pb)Sr2(Ca, Tl)Cu2O7–y with different conductive properties. Our analysis of their tetragonal crystal structure (space groupP4/m m m) from X-ray powder data revealed characteristic features such as Tl off-centering, multiple cations and partly vacant oxygen sites. We found that substitution of about 35% Pb2+ for Tl3+ in the TlO monolayers of the structure, accompanied by replacement of about 23% Tl3+ for Ca2+ in the perovskite-like layers, changed normalconducting into superconducting behavior, with a transition to zero resistivity at 76 K; normalconducting behavior was found for 25% Pb on Tl sites. Subtle differences in the comparably high levels of doping of the Cu–O pyramidal sheets with holes are assumed to be responsible for the different conductive properties observed. We suggest that an excessive hole concentration turns the compound from superconducting into metallic behavior.  相似文献   

15.
TheK-Shell Electron-Capture ProbabilityP K for the Electron Capture of139Ce has been measured using the coincidence method. The detectors used have been a NaJ(Tl)-detector with Be-window for the Lanthan-X-ray, a Ge(Li)- and a 76.2 mm Ø×76.2 mm-NaJ(Tl)-detector for the 166 keV--ray. The escape-effect of the Lanthan-X-ray in the NaJ(Tl)-detector was investigated. The experimental results areP K K= 0.726±0.010 andP K =0.801±0.034 using K=0.906±0.026.  相似文献   

16.
By the quenching of the delayed fluorescence (DF) of anthraquinone vapors by aliphatic amines (diethylamine, dibutylamine, cyclohexylamine) and pyridine the photoinduced processes proceeding with the participation of vibrationally excited triplet molecules of anthraquinone have been investigated. The DF quenchingrate constants K q varying from 1·106 sec–1·torr–1 in mixtures with diethylamine to 7·103 sec–1·torr–1 in mixtures with pyridine have been estimated. A correlation between the values of K q and the ionization potentials of foreign gases confirming the important role of interactions with charge transfer in the quenching of triplet molecules in the gas phase has been established. The influence of other relaxation processes on the DF quenching is considered. It is shown that the intermolecular vibrational relaxation in the T 1 triplet state leading to the establishment of relaxation equilibrium at a vibrational temperature T vib considerably increasing the medium temperature is the fastest process among the biomolecular processes (rate constants K col V > 106 sec–1·torr–1 > K q). The values of T vib and the vibrational energies E vib of the triplet molecules after the energy exchange in the collisional complex have been estimated. It has been concluded that the photochemical reaction yield is determined by the intermolecular processes proceeding in the T 1 state at a vibrational equilibrium characterized by high values of T vib. The influence of E vib of triplet molecules on the DF quenching rates at a photoinduced electron transfer is considered.  相似文献   

17.
Efficient CW intracavity frequency doubling of a diode-end-pumped Nd:GGG laser operating on 4 F 3/24 I 9/2 transitions at 937 nm has been demonstrated. A 10-mm-long BiB3O6(BiBO) crystal, cut for critical type I phase matching, was used for the intracavity frequency doubling of the laser. A maximum output power of 350 mW in the blue spectral range at 469 nm has been achieved at 18.3 W of pump power. The M2 factors are 1.18 and 1.29 in X and Y directions, respectively.  相似文献   

18.
Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to 2H11/24I15/2, 4S3/24I15/2 and 4F9/24I15/2 have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions. The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has been completed.  相似文献   

19.
The work of Lakowicz and Weber [Biochemistry 12, 4161 (1973)] demonstrated that molecular oxygen is a powerful quencher of tryptophan fluorescence in proteins. Here we report studies of the oxygen quenching of several proteins that have a single, internal tryptophan residue. Among these are apoazurin (Pseudomonas aeruginosa), asparaginase (Escherichia coli), ribonuclease T1 (Aspergillus oryzae), and cod parvalbumin. Both fluorescence intensity and phase lifetime quenching data are reported. By comparison of these data we find that there is a significant degree of apparent static quenching in these proteins. The dynamic quenching rate constants,k q, that we find are low compared to those for tryptophan residues in other proteins. For example, for apoazurin we find an apparentk q of 0.59×109 M –1 s–1 at 25°C. This value is the lowest that has been reported for the oxygen quenching of tryptophan fluorescence.  相似文献   

20.
A new three-dimensional thallium(I) supramolecular polymer, [Tl2(μ2-ATA)]n (1), [H2ATA = 2-aminoterephthalic acid], has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows one type of TlI ion with a low coordination number. Compound 1 was self-assembled from Tl⋯C, Tl⋯O and Tl⋯N secondary interactions in thallium(I) coordination and the active lone pair on TlI in this compound may be involved in donor bonding. Two sides of the aromatic ring of ATA2− anion have been involved in two types of secondary Tl⋯C approaches. Three samples of 1 were synthesized with three different concentrations of initial reagents under ultrasonic irradiation. The thermal stability of compound 1 samples were studied by thermo gravimetric (TG) and differential thermal analyses (DTA). These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).  相似文献   

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